In the medical field, it can be necessary to ensure that an inner part slides properly inside an outer tube, i.e. to ensure sliding with a minimum of friction while nevertheless benefiting from minimum clearance between the inner part and the outer tube.
By way of non-limiting example, the inner part may be the piston of a syringe, with the outer tube constituting the body of the syringe, or the inner part may be an inner tube such as the body of the syringe that is mounted to slide relative to an outer tube for covering one end of the inner tube, in particular for covering the needle of the syringe so as to avoid injury to the person handling the syringe after an injection.
In order to make it easier for the inner part to slide in the outer tube, a lubricating agent is generally provided on their facing walls. Lubrication ensures that friction is kept down to a minimum.
Nevertheless, the lubricating agent as used in this way constitutes a foreign body, the presence of which is often problematic in medical applications. There therefore exists a need for another technical solution that makes it possible to improve the sliding of a tube or an inner part inside an outer tube without it being necessary to have recourse to an additional lubricating agent.
The parts concerned (inner part, outer tube) are parts made of plastics material in industrial manner and on a very large scale. Given the large number of parts to be produced, the looked-for technical solution must be simultaneously simple, inexpensive, and involve each part during a length of time that is short; the solution must also be suitable for integrating in an industrial production process that is highly automated with very high rates of throughput.
The invention seeks to remedy those drawbacks by proposing a simple and reliable way of polishing the inside walls of cylindrical tubes, in particular tubes for medical use.